Progress Toward Poliomyelitis Eradication -- African Region, 1997

In 1988, the World Health Assembly established the goal of
eradicating poliomyelitis worldwide by 2000 (1). To achieve this
goal, the World Health Organization (WHO) promotes the
implementation of specific strategies (2,3). Eradicating polio from
the African continent is one of the remaining major challenges to
achieving global eradication by the target date. This report
summarizes progress in the African Region of WHO in 1997 with the
implementation of polio eradication strategies, and suggests that
polio eradication by 2000 remains a feasible target.

Reported routine coverage with three doses of oral poliovirus
vaccine (OPV3) among children aged less than 1 year is low in the
region overall but has increased from 47% in 1993 to 54% in 1996.
In 1996, 12 countries reported that less than 50% of children were
routinely vaccinated with OPV3. Of the largest and most populous
countries (Angola, Democratic Republic of Congo {DR Congo},
Ethiopia, and Nigeria), only Ethiopia improved routine coverage
(from 54% in 1995 to 67% in 1996), but coverage remained low in
1996 in Angola (42%), DR Congo (36%), and Nigeria (26%). All 24
countries of central and western Africa reported OPV3 coverage
levels at less than 60% in 1996, except Algeria (77%), Benin (80%),
The Gambia (97%), Senegal (80%), and Togo (82%).

During 1997 and the first quarter of 1998, a total of 36
countries in the region conducted National Immunization Days
(NIDs) * (Figure_1). These were the first NIDs for seven
countries
(Burundi, Guinea, Guinea-Bissau, Madagascar, Mali, Niger, and
Senegal). Because of political instability, NIDs could not be
conducted in Liberia, Republic of Congo, and Sierra Leone.
Vaccination coverage was reported at greater than or equal to 80%
for both rounds in all countries except Central African Republic
(81% and 73%), Gabon (78% and 82%), Kenya (76% and 80%), Lesotho
(67% and 65%), Mozambique (65% and 75%), Nigeria (72% and 91%),
Rwanda (73%, first round results only), and South Africa (81% and
76%) (Table_1). DR Congo conducted Subnational Immunization
Days
(SNIDs) ** in 47 cities (25% of the total population); coverage was
greater than 85% for both rounds.

Nigeria conducted NIDs in 1996 and 1997, with reported
coverage of 47% for the first and 75% for the second round in 1996,
and 72% and 91% for first and second rounds, respectively, in 1997.
In 1996, only five (16%) of 31 Nigerian states conducting NIDs
reported coverage levels of greater than 80% in both rounds. In
1997, a total of 16 (43%) of 37 states implementing NIDs achieved
greater than 80% coverage in both rounds. After 2 years of NIDs in
Nigeria, 15 states did not reach coverage of greater than 80% in
three of four rounds.

In 1996, a total of 1949 polio cases were reported from the
African region, with six countries accounting for 88% of cases:
Nigeria (942), Ethiopia (264), DR Congo (219), Uganda (121), Chad
(93), and Angola (81). In 1997, surveillance for acute flaccid
paralysis (AFP) had been established in all but eight countries in
the region (Burundi, Equatorial Guinea, Eritrea, Gabon, Liberia,
Mali, Rwanda, and Sierra Leone). The rate of AFP reporting in each
subregion (Western, Central, Southern, and Eastern) is low
(average: less than 0.2 nonpolio AFP cases per 100,000 children
aged less than 15 years). In two large countries that reported
rates of nonpolio AFP of greater than 0.4 per 100,000 (Ghana and
Uganda), the geographic distribution of AFP cases within the
country was uneven, and the percentage of AFP cases with two
specimens collected within 14 days of onset of paralysis remained
below the level of greater than or equal to 80% recommended by WHO.

In 1997, stool specimens collected from 73 persons with AFP in
countries in east Africa (Kenya, Tanzania, Uganda, and Zambia) were
negative for wild poliovirus, and no wild poliovirus was recovered
in southern Africa. Wild poliovirus was isolated from 33 AFP cases
from DR Congo and many countries in central and western Africa.
Wild poliovirus also was isolated after the first NIDs in the
Benin, Central African Republic, Chad, Cote d'Ivoire, and Nigeria.
Partial genomic sequencing of several wild poliovirus isolates
from countries neighboring DR Congo and Nigeria indicated that they
are related to viruses found in DR Congo and Nigeria.

Thirteen laboratories composing the African Regional Polio
Laboratory Network -- three regional reference laboratories and 10
intercountry and national laboratories -- were fully functional in
1997. The network supports 31 countries in the region. Seven
countries (Benin, Chad, DR Congo, Guinea, Guinea-Bissau, Ethiopia,
and Mali) contributed specimens to network laboratories for the
first time in 1997.

Editorial Note

Editorial Note: Countries of the African Region made substantial
progress toward polio eradication during 1996 and 1997 by 1)
achieving high coverage during 2 years of conducting NIDs, 2)
establishing AFP surveillance in many countries, and 3) creating a
functional regional laboratory network. In addition, high-level
political commitment and support for polio eradication in Africa
achieved in 1996 was sustained in 1997.

The two most important remaining reservoirs of wild poliovirus
are Nigeria and DR Congo. In Nigeria, several states have not yet
conducted one set of adequate double-round supplemental OPV
vaccination during NIDs, and reported routine vaccination coverage
with OPV3 was low during 1996. The first NIDs in DR Congo are
scheduled to begin in August 1998. Surveillance data and genomic
sequencing of viruses indicate that Nigeria and DR Congo are large
remaining virus reservoirs that frequently export wild poliovirus
to neighboring countries, making it more difficult for these
countries to become polio free.

AFP surveillance, although improving, remains at low levels.
High-quality AFP surveillance is essential to assess the impact of
polio eradication activities and, at later stages, to guide
interventions aimed at the interruption of wild poliovirus
transmission in the remaining virus reservoirs. Emphasis should be
placed on active surveillance at the provincial level to improve
the completeness and timeliness of detection, reporting, and
investigation of AFP cases and the collection of appropriate stool
specimens. Identifying personnel to conduct surveillance and
ensuring transportation and operating expenses at the provincial
level are important constraints.

AFP surveillance in the African Region has already provided
important epidemiologic information. Wild poliovirus was isolated
widely even after the first NIDs in west and central African
countries, indicating that wild poliovirus transmission had not yet
been interrupted in those areas. In comparison with eastern and
southern Africa, rapid success of polio eradication activities in
west and central Africa is constrained further by lower levels of
routine vaccination coverage in most countries. AFP surveillance
represents the first surveillance system being implemented
throughout the African Region that requires epidemiologic and
virologic investigation of individual cases; its procedures are
relatively complex and operationally demanding. Once fully
established, AFP surveillance can facilitate surveillance,
evaluation, and action for other diseases, including hemorrhagic
fever, yellow fever, meningitis, epidemic dysentery, and other
important and emerging diseases.

Polio eradication in Africa is receiving increased external
financial and technical support from Rotary International, WHO,
United Nations Children's Fund (UNICEF), U.S. Agency for
International Development (USAID), Basic Support for
Institutionalizing Child Survival (BASICS) project, CDC, the
government of Japan, the Canadian International Development Agency,
vaccine manufacturers, and other partners.

Polio eradication is achievable in the African Region by 2000
if the following constraints and potential obstacles are addressed:

rapid improvements of AFP surveillance in all countries with
endemic polio, 2) implemention of NIDs in the remaining countries
that have not conducted NIDs, and 3) implementation of polio
eradication strategies in countries experiencing internal strife or
civil war. In addition, substantial additional financial support is
needed, primarily for surveillance and to conduct activities in
countries experiencing civil unrest or war.

References

World Health Assembly. Global eradication of poliomyelitis by
the year
2000. Geneva, Switzerland: World Health Organization, 1988;
resolution
no. 41.28.

Mass campaigns over a short period (days to weeks) during which
two doses of OPV are administered to all children in the target age
group (usually 0-4 years) regardless of previous vaccination
history, with an interval of 4-6 weeks between doses.
** Focal mass campaigns in high-risk areas over a short period
(days to weeks) in which two doses of OPV are administered to all
children in the target age group, regardless of previous
vaccination history, with an interval of 4-6 weeks between doses.

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